As posted in that other thread, this is just an unsustained rumor.

Same one was floating around 2-3 years ago and it turned out that "Apple will use ARM in Macs" was just a controller chip for the touchbar and some security features.

Possible outcome:

Apple will continue on the effort on making IOS a full blown OS right to the point where the girl in the iPad-add asking "what is a computer" becomes reality.

At that point an iPadPro and beefed up AppleTV6 might compete with the MacBook and MacMini and if the big OSX-apps get a full version for iOS we might see the Mac fade away.

But not in in 2020.